Losing weight causes a decrease in insulin resistance. Sometimes you hit the magic weight and it can change dramatically. Some insulin resistance is caused by a certain type of stick fat that prevents insulin from binding to the cell once it joins with glucose. Glucose and insulin are very large molecules and together they are enormous. It does not take a lot to block it, I don't have much insulin resistance to speak of, but when I lose weight I still get more sensitive to insulin,

The why is always a battle. I'm going through the same, sudden need for more insulin, increase at 20% more per day and still increasing. I'm thinking maybe stress, maybe an added vitamin, decrease of alcohol, went back to standard time, a bit less exercise (colder weather), then maybe worrying because I can't instantly figure it out and my 70 yr. old body is reacting as quickly as I think it should. I think most of us have a battle from time to time with this, and I have over my 50 yrs. as Type 1. Don't be shy about asking for professional advise though!